Half bearing and sliding bearing

ABSTRACT

A semi-cylindrical half bearing for a sliding bearing includes at least one axial groove formed on its inner circumferential surface that includes a smooth groove surface formed back away from the inner circumferential surface toward a radially outer side. The half bearing further includes a plurality of axial narrow grooves and a plurality of circumferential narrow grooves that are formed further back away from the groove surface toward the radially outer side, and extend in circumferential and axial directions, respectively, so as to cross each other. A depth of the axial narrow groove from the groove surface is greater than a depth of the circumferential narrow groove from the groove surface, and a width of the axial narrow groove on the groove surface is greater than a width of the circumferential narrow groove on the groove surface.

BACKGROUND OF THE INVENTION (1) Field of the Invention

The present invention relates to a half bearing constituting a slidingbearing for supporting a crankshaft of an internal combustion engine.The present invention also relates to a cylinder-shaped sliding bearingincluding the half bearing for supporting the crankshaft of the internalcombustion engine.

(2) Description of Related Art

A crankshaft of an internal combustion engine is supported, at itsjournal portion, in a cylinder block bottom part of the internalcombustion engine via a main bearing consisting of a pair of halfbearings. In order to lubricate the main bearing, lubricating oildischarged by an oil pump is fed from an oil gallery formed in acylinder block wall into a lubricating oil groove formed along an innercircumferential surface of the main bearing, through a through-holeformed in a wall of the main bearing. A first lubricating oil path isformed to penetrate the journal portion in a diametrical directionthereof, so that openings formed at both ends of the first lubricatingoil path communicate with the lubricating oil groove of the mainbearing. Further, a second lubricating oil path extending through acrank arm portion is formed so as to branch from the first lubricatingoil path in the journal portion, and the second lubricating oil pathcommunicates with a third lubricating oil path formed to penetrate acrankpin in a diametrical direction thereof. Accordingly, thelubricating oil fed from the oil gallery in the cylinder block wall intothe lubricating oil groove formed on the inner circumferential surfaceof the main bearing through the through-hole is supplied also betweenthe crankpin and a slide surface of a connecting rod bearing consistingof a pair of half bearings, from an outlet opening which opens at an endof the third lubricating oil path, through the first lubricating oilpath, the second lubricating oil path, and the third lubricating oilpath (see JP H08-277831 A, for example). In this way, the oil issupplied between a surface of the crankshaft, and the slide surface ofthe main bearing and the slide surface of the connecting rod bearing.

Conventionally, in order to reduce seizure damage during sliding of acrankshaft on a sliding bearing such as a main bearing or a connectingrod bearing, there has been suggested to form a plurality of minutedepressions on slide surfaces of half bearings constituting the slidingbearing (see JP S58-149622 U, JP 2008-095721 A, and JP 2000-504089 A,for example).

BRIEF SUMMARY OF THE INVENTION

As described in JP S58-149622 U, JP 2008-095721 A, and JP 2000-504089 A,in a conventional half bearing in which a plurality of minutedepressions are formed on a slide surface, the motion in which the slidesurface of the half bearing and a surface of a crankshaft come close toeach other is repeated during operation of an internal combustion engine(particularly, under an operation condition where the crankshaft rotatesat high speed), so that oil in the depressions is compressed and becomeshigh in temperature at the moment when the slide surface and thecrankshaft surface come closest to each other. When the oil which hasbecome high in temperature in the depressions flows out to a spacebetween the slide surface of the half bearing and the crankshaftsurface, the slide surface rises in temperature and becomes easilyseized. Further, there has been a problem that the viscosity of oildecreases, the slide surface and the crankshaft surface become directlyin contact with each other, and thereby damage becomes readily caused.

Accordingly, an object of the present invention is to provide a halfbearing constituting a sliding bearing for a crankshaft of an internalcombustion engine, that hardly causes seizure damage by discharging oilhaving become high in temperature to the outside during operation of theinternal combustion engine.

A half bearing according to the present invention is adapted toconfigure a sliding bearing for supporting a crankshaft of an internalcombustion engine. This half bearing has a semi-cylindrical shape, andincludes an inner circumferential surface including a slide surface. Thehalf bearing also includes at least one axial groove formed on the innercircumferential surface. The axial groove includes a smooth groovesurface formed back away from the inner circumferential surface toward aradially outer side of the half bearing, and the groove surface forms aconvex curve toward the radially outer side in a sectional viewperpendicular to the axial direction of the half bearing, and alsoforms, in a section parallel to the axial direction, a straight lineextending in the axial direction. The half bearing further includes, onthe groove surface, a plurality of circumferential narrow grooves and aplurality of axial narrow grooves formed back away from the groovesurface toward the radially outer side, and the plurality ofcircumferential narrow grooves and the plurality of axial narrow groovesextend in a circumferential direction and the axial direction of thehalf bearing, respectively, so as to intersect each other. A depth ofeach of the axial narrow grooves from the groove surface of the axialgroove is greater than a depth of each of the circumferential narrowgrooves from the groove surface of the axial groove, and a width of eachof the axial narrow grooves on the groove surface of the axial groove isgreater than a width of each of the circumferential narrow grooves onthe groove surface of the axial groove.

In one embodiment of the present invention, the depth of the axialgroove that is the length from the inner circumferential surface to thedeepest portion of the groove surface is preferably 2 to 50 μm. Thecircumferential length of the axial groove is preferably within a rangeof about 0.5 to 10° as a central angle of the entire inner circumferenceof the half bearing (e.g. when the inner diameter of the half bearing ofthe internal combustion engine is (φ50 mm, the circumferential length ofthe axial groove is preferably about 1 to 4 mm).

In one embodiment of the present invention, a depth of each of thecircumferential narrow grooves from the groove surface of the axialgroove is preferably 0.05 to 3 μm. A width of each of thecircumferential narrow grooves on the groove surface of the axial grooveis preferably 5 to 85 μm. Further, a pitch of the circumferential narrowgrooves is preferably 5 to 100 μm.

In one embodiment of the present invention, a depth of each of the axialnarrow grooves from the groove surface of the axial groove is preferably0.3 to 10 μm. A width of each of the axial narrow grooves on the groovesurface of the axial groove is preferably 10 to 150 μm. Further, a pitchof the axial narrow grooves is preferably 10 to 200 μm.

In one embodiment of the present invention, a plurality of the axialgrooves may be formed on the inner circumferential surface of the halfbearing.

In one embodiment of the present invention, the plurality of axialgrooves may be formed on the inner circumferential surface of the halfbearing at substantially equal intervals in the circumferentialdirection.

In one embodiment of the present invention, the axial groove does notreach any of the axial end surfaces of the half bearing, and thereforemay not open at any end surface.

The present invention also relates to a cylindrical sliding bearing thatincludes the half bearing described above, which serves to bear acrankshaft of an internal combustion engine. In other words, thissliding bearing is constituted of a pair of half bearings at least oneof which is the half bearing described above.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic view illustrating a bearing device of a crankshaftof an internal combustion engine;

FIG. 2 is a view illustrating movement of a crankpin relative to a pairof half bearings;

FIG. 3 is a view in which a half bearing according to a first embodimentof the present invention is seen from an axial direction;

FIG. 4 is a plan view in which the half bearing illustrated in FIG. 2 isseen from an inner circumferential surface side, and an enlarged view ofa groove surface of an axial groove;

FIG. 5 is a schematic perspective view illustrating the groove surfacein an enlarged form;

FIG. 6 is a circumferential sectional view of the axial groove alongline A-A of FIG. 4;

FIG. 7 is an axial sectional view of the axial groove along line B-B ofFIG. 4;

FIG. 8 is an enlarged sectional view illustrating FIG. 7 in an enlargedform;

FIG. 9 is an enlarged sectional view illustrating FIG. 6 in an enlargedform;

FIG. 10 is a view illustrating the flow of oil in the axial grooveduring high-speed rotation of the crankshaft;

FIG. 11 is a view illustrating the flow of oil in the axial grooveduring low-speed to medium-speed rotation of the crankshaft;

FIG. 12 is a view in which a pair of half bearings according to a secondembodiment of the present invention and the crankpin are seen from theaxial direction;

FIG. 13 is a plan view in which the half bearing illustrated in FIG. 12is seen from the inner circumferential surface side;

FIG. 14 is a view in which a pair of half bearings according to a thirdembodiment of the present invention and the crankpin are seen from theaxial direction;

FIG. 15 is a plan view in which the half bearing illustrated in FIG. 14is seen from the inner circumferential surface side;

FIG. 16 is a view in which a pair of half bearings according to a fourthembodiment of the present invention and a crankpin are seen from theaxial direction; and

FIG. 17 is a plan view in which the half bearing illustrated in FIG. 16is seen from the inner circumferential surface side.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the invention of the present applicationwill be described with reference to the drawings.

A bearing device 1 of an internal combustion engine is schematicallyillustrated in FIG. 1. This bearing device 1 includes a journal portion6 supported by a bottom part of a cylinder block 8, a crankpin 5 whichis formed integrally with the journal portion 6 and thus rotates aroundthe journal portion 6, and a connecting rod 2 which transmits reciprocalmotion from the internal combustion engine to the crankpin 5. Thebearing device 1 further includes, as sliding bearings which supports acrankshaft, a main bearing 4 which rotatably supports the journalportion 6 and a connecting rod bearing 3 which rotatably supports thecrankpin 5.

It should be noted that the crankshaft includes a plurality of journalportions 6 and a plurality of crankpins 5, but herein, one journalportion 6 and one crankpin 5 are illustrated and described forconvenience of explanation. In FIG. 1, regarding a positionalrelationship in a depth direction of its drawing paper, the journalportion 6 is located on the far side of the paper surface, and thecrankpin 5 is located on the near side thereof.

The journal portion 6 is supported by a cylinder block bottom part 81 ofthe internal combustion engine via the main bearing 4 configured by apair of half bearings 41 and 42. In the half bearing 41 on the upperside in FIG. 1, an oil groove 41 a is formed over the entire length ofthe inner circumferential surface. The journal portion 6 has alubricating oil path 6 a formed to penetrate in the radial direction,and when the journal portion 6 rotates in an arrow X direction, inletopenings 6 c at both ends of the lubricating oil path 6 a alternatelycommunicate with the oil groove 41 a of the main bearing 4.

The crankpin 5 is supported by a large-end housing 21 of the connectingrod 2 (configured by a rod-side large-end housing 22 and a cap-sidelarge-end housing 23), via the connecting rod bearing 3 configured by apair of half bearings 31 and 32.

A second lubricating oil path 5 a branching from the first lubricatingoil path 6 a of the journal portion 6 and passing through a crank armportion (not illustrated) is formed, and the second lubricating oil path5 a communicates with a third lubricating oil path 5 b formed topenetrate in the radial direction of the crankpin 5.

Therefore, as described above, lubricating oil discharged from an oilpump is fed into the oil groove 41 a formed along the innercircumferential surface of the main bearing 4, from an oil galleryformed in a cylinder block wall through a through-hole formed in a wallof the main bearing 4, and supplied to a space formed between thejournal portion 6 and the main bearing 4.

On the other hand, the lubricating oil is also supplied to a spaceformed between the crankpin 5 and the connecting rod bearing 3 from anoutlet 5 c located at the end of the third lubricating oil path 5 bthrough the first lubricating oil path 6 a, the second lubricating oilpath 5a, and the third lubricating oil path 5 b.

In general, the main bearing 4 and the connecting rod bearing 3 bear adynamic load from the crankshaft by generating pressure in oil betweenthe slide surfaces of the bearings and the crankshaft surfaces (thesurfaces of the journal portion 6 and the crankpin 5). During theoperation of the internal combustion engine, the magnitude and directionof the load on the slide surfaces of the main bearing 4 and theconnecting rod bearing 3 vary all the time, and the central axes of thejournal portion 6 and the crankpin 5 move while decentering relative tothe bearing central axes of the main bearing 4 and the connecting rodbearing 3 so as to generate oil film pressure balancing with the load.Thus, a bearing clearance (a space between the crankshaft surface andthe slide surface) of the main bearing 4 and the connecting rod bearing3 always changes at any position of the slide surface. For example, in afour-cycle internal combustion engine, the load on the connecting rodbearing 3 and the main bearing 4 is maximized in a combustion stroke. Inthis combustion stroke, as shown in FIG. 2, the crankpin 5 supported bythe connecting rod bearing 3 moves in a direction (arrow Q) toward aslide surface 70 near the circumferential central portion of the halfbearing 31 on the upper side of the paper surface, whereby the surfaceof the crankpin 5 comes closest to the slide surface 70 near thecircumferential central portion of the half bearing 31, and a load isapplied in this movement direction.

It should be noted that in the main bearing 4 being in a combustionstroke, the load is applied in a direction toward the slide surface nearthe circumferential central portion of the half bearing 42 set in abearing cap 82 on the lower side of the paper surface illustrated inFIG. 1, and the surface of the journal portion 6 comes closest to theslide surface near the circumferential central portion of the halfbearing 42 on the lower side.

In a half bearing according to a conventional technique in which aplurality of minute depressions are formed on a slide surface, the slidesurface of the half bearing having the minute depressions and acrankshaft surface move so as to relatively come close to each otherfrom a separated state. When the surfaces come closest to each other,oil in the depressions is compressed and becomes high in pressure, andthus high in temperature, and flows out into a space between the slidesurface and the crankshaft surface. Thus, the temperature of the slidesurface rises, and seizure is easily caused. Further, due to decrease inthe viscosity of the oil, the slide surface and the crankshaft surfacedirectly contact with each other, and damage is more likely to becaused.

The present invention copes with such a problem of the conventionaltechnique. The embodiments in which the half bearing according to thepresent invention is applied to a connecting rod bearing are describedbelow. However, it will be appreciated that the half bearing accordingto the present invention is not exclusively applied to a connecting rodbearing, and may be applied to a main bearing.

Both of a pair of half bearings constituting the connecting rod bearing3 or the main bearing 4 may be the half bearings according to theinvention, or one of the pair of half bearings may be the half bearingaccording to the invention while the other may be a conventional halfbearing having no axial groove on a slide surface.

First Embodiment

FIG. 3 is a view in which a first embodiment of the half bearings 31 and32 according to the present invention is seen from the axial direction.The connecting rod bearing 3 is configured by bringing circumferentialend surfaces 76 of the half bearings 31 and 32 into abutment with eachother, and combining the half bearings 31 and 32 into a cylindricalshape as a whole. In the present embodiment, a cylindrical innercircumferential surface 7 includes the slide surface 70.

As illustrated in FIGS. 2 and 3, the wall thickness of the half bearings31 and 32 is preferably constant along the circumferential direction.However, the wall thickness may be maximum in the circumferentialcentral portion, and continuously decrease toward both circumferentialend surfaces 76.

FIG. 4 is a view in which each of the half bearings 31 and 32 having oneaxial groove 71 disposed on the slide surface 70 is seen from the slidesurface 70 side. However, the present invention is not limited to thisembodiment. For example, a plurality of axial grooves 71 may be formedin the axial direction of the slide surface 70. It should be noted that,for ease of understanding, the axial grooves 71 are drawn non-scale ineach drawings.

As illustrated in FIGS. 3 and 4, the axial groove 71 has a smooth groovesurface 71S back away from the slide surface 70 toward the radiallyouter side. As illustrated in the enlarged view of FIG. 4, in the groovesurface 71S, there are formed a plurality of circumferential narrowgrooves 71C extending in the circumferential direction of each of thehalf bearings 31 and 32, and a plurality of axial narrow grooves 71Aextending in the axial direction. Therefore, it will be appreciated thatthe extension direction of each of the circumferential narrow grooves71C is perpendicular to the extension direction of each of the axialnarrow grooves 71A.

It should be noted that the plurality of circumferential narrow grooves71C extend in a direction parallel to the circumferential direction ofeach of the half bearings 31 and 32, but are permitted to slightly tilt(1° at the maximum) relative to the circumferential direction.Similarly, the plurality of axial narrow grooves 71A extend in adirection parallel to the axial direction of each of the half bearings31 and 32, but are permitted to slightly tilt (1° at the maximum)relative to the axial direction.

Each of the circumferential narrow grooves 71C preferably extends froman edge of the axial groove 71 to an opposite edge, and each of theaxial narrow grooves 71A preferably extends from one axial end surface77 of each of the half bearings 31 and 32 to the other axial end surface77.

FIG. 5 is a schematic perspective view illustrating the groove surface71S in an enlarged manner. As will be appreciated, the smooth groovesurface 71S of the axial groove 71 comprises a plurality of smallsurfaces 71S′ formed between the plurality of circumferential narrowgrooves 71C and the plurality of axial narrow grooves 71A, and thereforethe groove surface 71S and the plurality of circumferential narrowgrooves 71C are alternately disposed along line B-B illustrated in FIG.4. Similarly, the groove surface 71S and the plurality of axial narrowgrooves 71A are alternately disposed along line A-A illustrated in FIG.4. Each of the small surfaces 71S′ is a smooth surface having no grooveor protrusion formed thereon, but may have a minute depression andprojection (that are sufficiently small as compared with thecircumferential narrow grooves and the axial narrow grooves) presentthereon.

FIG. 6 is an enlarged view of the A-A section of the axial groove 71illustrated in FIG. 4. FIG. 7 is an enlarged view of the B-B section ofthe axial groove illustrated in FIG. 4. A depth D of the axial groove 71from the slide surface 70 illustrated in FIG. 6 (a depth from the slidesurface 70 adjacent to the axial groove 71 to the deepest portion of theaxial narrow groove 71A) is preferably 2 to 50 μm, and more preferably 2to 25 μm. A circumferential length L of the axial groove 71 ispreferably within an extent of about 0.5 to 10° of the central anglewith respect to the entire inner circumference of the half bearing 31(for example, when the inside diameter of the half bearing of theinternal combustion engine is φ50 mm, the circumferential length L ofthe axial groove 71 is preferably about 1 to 4 mm).

When the depth D of the axial groove 71 is too small, the quantity ofhigh-temperature oil discharged to the outside of the bearing is alsotoo small. On the contrary, when the depth D is too great, the quantityof oil discharged to the outside of the bearing is also too great, andthereby the oil supply to the slide surface becomes extremely reduced.When the circumferential length L of the axial groove 71 is too short,the quantity of high-temperature oil discharged to the outside of thebearing is too small. On the contrary, when the circumferential length Lof the axial groove 71 is too long, the quantity of oil discharged tothe outside of the bearing is too great, and the oil supply to the slidesurface becomes extremely reduced.

FIG. 8 is an enlarged view of the B-B section of the axial groove 71illustrated in FIG. 7. A depth DC of the circumferential narrow groove71C illustrated in FIG. 8 (a depth from the groove surface 71S adjacentto the circumferential narrow groove 71C to the deepest portion of thecircumferential narrow groove 71C in a section perpendicular to thelongitudinal direction of the circumferential narrow groove 71C) ispreferably 0.05 to 3 μm. The depth DC of the circumferential narrowgroove 71C is made smaller than the depth D of the axial groove 71.

A width WC of the circumferential narrow groove 71C (the axial length ofthe circumferential narrow groove 71C on the groove surface 71S) ispreferably 5 to 85 μm. Further, an axial pitch PC of the circumferentialnarrow grooves 71C on the groove surface 71S of the axial groove 71 (anaxial distance between the deepest portions of the adjacentcircumferential narrow grooves 71C) is preferably 5 to 100 μm.

When the depth DC or the width WC of the circumferential narrow groove71C is out of the dimensional range described above and too small, theoil flowing from the circumferential narrow groove 71C during thelow-speed to medium-speed rotation of a crankshaft of an internalcombustion engine is extremely reduced, and the oil supply to the slidesurface 70 becomes insufficient. On the contrary, when the depth DC orthe width WC is too great, the high-temperature oil in the axial groove71 is fed to the slide surface 70 in great quantity during thehigh-speed rotation of the crankshaft of the internal combustion engine,and discharge of the oil to the outside becomes difficult.

FIG. 9 is an enlarged view of the A-A section of the axial groove 71illustrated in FIG. 6. A depth DA of the axial narrow groove 71Aillustrated in FIG. 9 (a depth from the groove surface 71S adjacent tothe axial narrow groove 71A to the deepest portion of the axial narrowgroove 71A in a section perpendicular to the longitudinal direction ofthe axial narrow groove 71A) is preferably 0.3 to 100 μm. The depth DAof the axial narrow groove 71A is made smaller than the depth D of theaxial groove 71.

A width WA of the axial narrow groove 71A (the circumferential length ofthe axial narrow groove 71A on the groove surface 71S) is preferably 10to 150 μm. Further, a circumferential pitch PA of the axial narrowgrooves 71A on the groove surface 71S of the axial groove 71 (acircumferential distance between the deepest portions of the adjacentaxial narrow grooves 71A) is preferably 10 to 200 μm.

When the depth DA or the width WA of the axial narrow groove 71A is outof the dimensional range described above and too small, discharge of thehigh-temperature oil in the axial groove 71 to the outside becomesdifficult during the high-speed rotation of the crankshaft of theinternal combustion engine, and the oil is fed to the slide surface 70.On the contrary, when the depth DA or the width WA is too great, the oilin the axial groove 71 is discharged to the outside too much during thelow-speed to medium-speed rotation of the crankshaft of the internalcombustion engine, and the oil supply to the slide surface 70 becomesinsufficient.

The groove surface 71S (the surface of the axial groove excluding thecircumferential narrow groove and the axial narrow groove) describes acurve expanding toward the radially outer side of each of the halfbearings 31 and 32, i.e., a radially outwardly convex curve, in asection (the A-A section in FIG. 4) perpendicular to the axial directionof each of the half bearings 31 and 32 (see FIG. 6). It should be notedthat the circumferential narrow groove 71C and the axial narrow groove71A are formed also to expand to the radially outer side of each of thehalf bearings 31 and 32 in a section perpendicular to the axialdirection of each of the half bearings 31 and 32. In the cross-section(the B-B section in FIG. 4) parallel to the axial direction of each ofthe half bearings 31 and 32, the groove surface 71S describes a straightline which is located back away from the slide surface 70 toward theradially outer side of the half bearings 31 and 32, and extends in theaxial direction (see FIG. 7).

When the pitch PC of the circumferential narrow grooves 71C and thepitch PA of the axial narrow grooves 71A are out of the dimensionalrange described above and too great, and the width WC of thecircumferential narrow groove 71C and the width WA of the axial narrowgroove 71A are too small, the smooth groove surface 71S becomesextremely large. In this case, pressure is generated in oil on thegroove surface 71S when the slide surface 70 and the crankpin 5 comeclosest to each other. Regardless, since the width WC of thecircumferential narrow groove 71C is small, the oil supply to the slidesurface 70 becomes small during the low-speed to medium-speed rotationof the crankshaft. Moreover, since the width WA of the axial narrowgroove 71A is small, the discharge quantity of the oil which has becomehigh in temperature during the high-speed rotation of the crankshaftbecomes small Thus, when the groove surface 71S becomes extremely large,the slide surface 70 and the crankpin 5 more easily come into directcontact with each other.

On the contrary, when the pitch PC of the circumferential narrow grooves71C and the pitch PA of the axial narrow grooves 71A are out of thedimensional range described above and too small, and the width WC of thecircumferential narrow groove 71C and the width WA of the axial narrowgroove 71A are too great, the smooth groove surface 71S becomesextremely small. In this case, the range in which the pressure isgenerated is small, bearing of the crankpin 5 becomes insufficient, andtherefore, the slide surface 70 and the crankpin 5 more easily come intodirect contact with each other.

When there is no groove surface 71S (the axial narrow grooves 71A aredisposed so as to directly range in the circumferential direction,and/or the circumferential narrow grooves 71C are disposed so as todirectly range in the axial direction), the oil is not easily compressedin the axial groove 71, and the pressure is not easily generated, duringthe closest contact between the slide surface 70 and the crankpin 5.Therefore, the slide surface 70 and the crankpin 5 more easily come intodirect contact with each other.

In the present embodiment, the axial narrow groove 71A is formed in sucha way that the depth DA thereof from the groove surface 71S of the axialgroove 71 is constant along the extension direction (longitudinaldirection) of the axial narrow groove 71A, and the width WA is constantalong the extension direction of the axial narrow groove 71A. It shouldbe noted that the sectional shape of the axial narrow groove 71A ispreferably a U-shape (see FIG. 9), but is not limited to the U-shape,and may have any other shape.

However, the depth DA or the width WA of the axial narrow groove 71A mayvaries along the extension direction of the axial narrow groove 71A. Inthis case, the depth DA and the width WA of the axial narrow groove 71Aare defined by the maximum groove depth and the maximum groove width asdescribed above, and these maximum values are preferably within thedimensional range described above.

In the present embodiment, the circumferential narrow groove 71C isformed in such a way that the depth DC thereof from the groove surface71S of the axial groove 71 is constant along the extension direction(longitudinal direction) of the circumferential narrow groove 71C exceptfor a circumferential end, and the width WC is constant along theextension direction of the circumferential narrow groove 71C. It shouldbe noted that the sectional shape of the circumferential narrow groove71C is also preferably a U-shape (see FIG. 8), but is not limited to theU-shape, and may have any other shape.

However, the depth DC or the width WC of the circumferential narrowgroove 71C may vary along the extension direction of the circumferentialnarrow groove 71C. In this case, the depth DC and the width WC of thecircumferential narrow groove 71C are defined by the maximum groovedepth and the maximum groove width of the circumferential narrow groove71C as described above, and these maximum values are preferably withinthe dimensional range described above.

The connecting rod bearing 3 according to the present embodiment isformed by bringing the circumferential end surfaces 76 of the pair ofhalf bearings into abutment with each other, and combining the halfbearings into a cylinder shape as a whole. Both of the pair of halfbearings are preferably the half bearings 31 and 32 according to thepresent invention, but only one of the pair of half bearings may be thehalf bearing 31 or 32 according to the present invention. Each of thehalf bearings 31 and 32 may have a slide layer which is a Cu bearingalloy or an Al bearing alloy. Alternatively, each of the half bearings31 and 32 may have a slide layer of a Cu bearing alloy or an Al bearingalloy on a back metal layer made of an Fe alloy. A surface portion madeof one kind of metal selected from the group consisting of Bi, Sn, andPb softer than a bearing alloy, or an alloy including these metals asmain constituents, or a surface portion made of a resin compositionincluding synthetic resin as a main constituent may be provided on theslide surface 70 and the groove surface 71S (the surface of the slidelayer) on the cylindrically-shaped inner circumferential surface.However, the groove surface 71S of the axial groove 71 preferably has nosuch surface portion. This is because when the groove surface 71S of theaxial groove 71, or the surfaces of the circumferential narrow groove71C and the axial narrow groove 71A are soft, plastic deformation,excessive elastic deformation or the like occurs in the smooth groovesurface 71S of the axial groove 71, so that sufficient oil pressure isnot generated, and the slide surface 70 and the crankpin 5 more easilycome into contact with each other.

As described above, in the half bearing according to the presentinvention, the axial groove 71 having the smooth groove surface 71S isformed on the slide surface 70, and the plurality of circumferentialnarrow grooves 71C and the plurality of axial narrow grooves 71A areformed on the groove surface 71S. The reason that seizure damage isreduced by this half bearing is described below.

In an operation condition where a crankshaft of an internal combustionengine rotates at high speed, the slide surface 70 of the half bearing31 having the axial groove 71 and the surface of the crankpin 5 act torelatively come close to each other from a separated state. FIG. 2illustrates a state in which the slide surface 70 and the surface of thecrankpin 5 come closest to each other. In this instance, oil in theaxial groove 71 is compressed and becomes high in pressure, therefore,high in temperature, but the high-temperature oil is guided to the axialnarrow groove 71A formed on the surface of the axial groove 71, and thenmostly discharged to the outside in the axial direction, as indicated byarrows M in FIG. 10 in which the half bearing 31, 32 is seen from theinner circumferential surface side thereof.

Thus, the high-temperature oil does not flow out to the slide surface70, a temperature rise of the slide surface 70 can be restrained, andtherefore, seizure damage can be reduced. In this instance, the depth ofthe axial narrow groove 71A needs to be greater than the depth of thecircumferential narrow groove 71C. If the circumferential narrow groove71C is deeper than the axial narrow groove 71A, oil that has become highin temperature in the axial groove 71 is guided to the circumferentialnarrow groove 71C, flows to the slide surface, and is not easilydischarged to the outside. Thus, in order for oil to be guided to theaxial narrow groove 71A, and easily discharged to the outside, therelation: the depth of the axial narrow groove 71A>the depth of thecircumferential narrow groove 71C is needed.

In a (normal) operation condition of the internal combustion enginewhere the crankshaft rotates at low speed or medium speed, a clearancebetween the slide surface 70 and the surface of the crankpin 5 is largeeven during an action in which the slide surface 70 and the surface ofthe crankpin 5 come close to each other, and oil in the axial groove 71does not become high in temperature. In this instance, thecircumferential narrow groove 71C is also formed on the groove surface71S of the axial groove 71, and therefore serves as resistance to theoutward discharge of oil at the axial end of the axial groove 71, andthe oil is guided to the circumferential narrow groove 71C and then fedto the slide surface 70, as indicated by arrows N in FIG. 11. Therefore,enough oil is supplied to the slide surface 70, which can make itdifficult to cause seizure damage.

When the axial groove 71 only includes the groove surface 71S, or whenonly the axial narrow groove 71A is formed in the groove surface 71S,and the circumferential narrow groove 71C is not formed, oil is alsodischarged to the outside by the axial groove 71 during an action inwhich the slide surface 70 and the surface of the crankpin 5 come closeto each other in a (normal) operation condition of the internalcombustion engine where the crankshaft rotates at low speed or mediumspeed.

When only the circumferential narrow groove 71C is formed on the groovesurface 71S of the axial groove 71, and the axial narrow groove 71A isnot formed, oil that has become high in temperature in the axial groove71 in an operation condition of the internal combustion engine where thecrankshaft continuously rotates at high speed is fed to the slidesurface side by the circumferential narrow groove 71C, and discharge ofthe oil to the outside becomes difficult.

When the circumferential narrow groove 71C is deeper than the axialnarrow groove 71A, oil that has become high in temperature in the axialgroove 71 is guided to the circumferential narrow groove 71C and thusflows to the slide surface, and is therefore not easily discharged tothe outside.

The axial groove 71 has the smooth groove surface 71S, and thus oil inthe axial groove 71 is compressed and becomes high in pressure theinstance that the slide surface 70 and the surface of the crankpin 5come closest to each other. However, oil that has become instantaneouslyhigh in pressure in the axial groove 71 prevents the slide surface 70adjacent to the axial groove 71 and the surface of the crankpin 5 fromdirectly contacting each other.

Second Embodiment

Another non-limited embodiment of the present invention is describedbelow.

FIGS. 12 and 13 illustrate the half bearing 31 in which a plurality ofaxial grooves 71 are provided over the entire inner circumferentialsurface. The inner circumferential surface 7 of each of the halfbearings 31 and 32 includes the slide surface 70, and a crush relief 72formed adjacent to each of both circumferential end surfaces 76. Othercomponents are the same as those of the half bearings 31 and 32 alreadydescribed.

In this embodiment, the plurality of axial grooves 71 having the sameshape and dimension are provided at substantially equal intervals insubstantially the entire inner circumferential surface 7. It should benoted that FIG. 13 is a plan view in which the semi-cylindrical halfbearing 31 is seen from the inner circumferential surface side, andthus, the shape of the axial groove 71 near the circumferential endsurface 76 is drawn in a distorted form. In FIG. 13, the circumferentialnarrow groove 71C and the axial narrow groove 71A are omitted, and thusnot illustrated.

The crush relief 72 means a surface formed by reducing the thickness ofa wall portion from the original slide surface 70 in the radialdirection in a circumferential end region of each of the half bearings31 and 32. For example, the crush relief 72 is formed in order to absorbdisplacement or deformation of the circumferential end surface 76 of thehalf bearings 31 and 32 that can occur when the pair of half bearings 31and 32 are set to the connecting rod 2. Therefore, the curvature centerposition of the surface of the crush relief 72 is different from thecurvature center position of other regions of the slide surface 70 (seeSAE J506 (item 3.26 and item 6.4), DIN1497, section 3.2, JIS D3102).Generally, in the case of a bearing of a small internal combustionengine for a passenger car, the depth of the crush relief 72 (thedistance from the original slide surface to the crush relief 72) on thecircumferential end surface of a half bearing is approximately 0.01 to0.05 mm.

In a high-rotation type engine among four-cycle internal combustionengines, a crankshaft tends to whirl, and the slide surface 70 and thesurface of the crankpin 5 come close to each other over the entirecircumference of the half bearings 31 and 32, easily resulting in directcontact. Since the axial groove 71 of each of the half bearings 31 and32 according to the present embodiment is provided over the entirecircumference of the half bearing 31, there are more places where oilthat has become high in temperature in the axial groove 71 isdischarged, even in an operation condition of the internal combustionengine where the crankshaft continuously rotates at high speed.Therefore, a temperature rise of the slide surface 70 can be restrained,and it becomes difficult for the slide surface 70 of the half bearing 31and the surface of the crankpin 5 to directly contact each other.

It should be noted that the formation range of the axial groove 71 isnot limited to only a range near the circumferential central portion ofthe inner circumferential surface 7 of the half bearing 31, and theaxial groove 71 may be formed in any circumferential range. Moreover,the axial groove 71 may be formed in the crush relief 72. Although fiveaxial grooves 71 are drawn in FIGS. 12 and 13, the present invention isnot limited thereto.

Third Embodiment

FIGS. 14 and 15 illustrate the half bearing 31 in which a plurality ofaxial grooves 71 are provided in a part of the inner circumferentialsurface in the circumferential direction. The inner circumferentialsurface 7 of each of the half bearings 31 and 32 includes the slidesurface 70, and the crush relief 72 formed adjacent to both of thecircumferential end surfaces 76. Other components are the same as thoseof the half bearings 31 and 32 already described. It should be notedthat in FIG. 14, the circumferential narrow groove 71C and the axialnarrow groove 71A are omitted, or not illustrated.

In this embodiment, the plurality of axial grooves 71 having the sameshape and dimension are provided in a part of the inner circumferentialsurface 7 in the circumferential direction. It should be noted that FIG.15 is a plan view in which the semi-cylindrical half bearing 31 is seenfrom the inner circumferential surface side, and thus, the shape of theaxial groove 71 near the circumferential end surface 76 is drawn in adistorted form.

In the half bearing 31 according to the present embodiment, theplurality of axial grooves 71 are provided in a part of the innercircumferential surface 7, and therefore, there are more places whereoil that has become high in temperature in the axial groove 71 isdischarged, even in an operation condition of an internal combustionengine where a crankshaft continuously rotates at high speed. Therefore,a temperature rise of the slide surface 70 can be restrained. Moreover,as compared with the case where the axial groove 71 is formed over theentire circumference of the inner circumferential surface 7, thecapability of supporting the crankpin 5 by the slide surface 70 is high.Therefore, it becomes difficult for the slide surface 70 of the halfbearing 31 and the surface of the crankpin 5 to directly contact eachother.

It should be noted that in the case of an internal combustion enginehaving a specification in which a part closer to the circumferentialcentral portion of the inner circumferential surface 7 of each of thehalf bearings 31 and 32 more easily contact the surface of the crankpin5 during the operation, the plurality of axial grooves 71 may bedisposed close to the circumferential central portion of the innercircumferential surface 7 of the half bearing 31, in contrast to thepresent embodiment.

As described above, the position and number of the axial grooves 71 canbe changed depending on the specification of an internal combustionengine. The axial grooves 71 may be formed in the crush relief 72.Although six axial grooves 71 are drawn in FIGS. 14 and 15, the presentinvention is not limited thereto.

Fourth Embodiment

FIGS. 16 and 17 illustrate an embodiment in which the axial groove 71does not reach the axial end surface 77 of the half bearing 31, and theaxial groove 71 is blocked in the axial direction. Thus, excessivedischarge of oil is prevented.

It should be noted that in FIG. 17, the circumferential narrow groove71C and the axial narrow groove 71A are omitted, and not illustrated.Although one axial groove 71 is drawn in FIGS. 16 and 17, this is mereone example, and the configuration that is blocked in the axialdirection can also be applied to any of the embodiments described above.In the present embodiment, the axial groove 71 is formed in such a waythat the center of its axial length L2 coincides with the center of anaxial length L1 of the half bearing 31. Moreover, the axial groove 71 ispreferably formed in such a way that its axial length L2 is 70% to 95%of the axial length L1 of the half bearing 31.

In the present embodiment, the circumferential narrow groove 71C isformed in such a way that the depth DC thereof from the groove surface71S of the axial groove 71 is constant over the extending direction(longitudinal direction) of the circumferential narrow groove 71C exceptfor a circumferential end, and the width WC is constant over theextending direction of the circumferential narrow groove 71C. It shouldbe noted that the sectional shape of the circumferential narrow groove71C is preferably U-shaped, but is not limited to a U-shape, and mayhave any other shape.

However, the depth DC or the width WC of the circumferential narrowgroove 71C may vary along the extending direction of the circumferentialnarrow groove 71C. In this case, the depth DC and the width WC of thecircumferential narrow groove 71C have the maximum groove depth and themaximum groove width of the circumferential narrow groove 71C, themaximum values of which are preferably within the dimensional rangedescribed above.

Although the above description has been given using an example in whichthe half bearing according to the present invention is applied to aconnecting rod bearing that bears a crankpin of a crankshaft of aninternal combustion engine, the half bearing according to the presentinvention can also be applied to one or both of a pair of half bearingsconstituting a main bearing that bears a journal portion of thecrankshaft. Moreover, the half bearing may further have, for example, anoil hole or an oil groove, and have, on the entire slide surface exceptfor the axial groove 71, a plurality of microgroove portions extendingin the circumferential direction of the half bearing.

1. A half bearing having a semi-cylindrical shape and adapted toconstitute a sliding bearing for supporting a crankshaft of an internalcombustion engine, the half bearing comprising at least one axial grooveformed on an inner circumferential surface thereof, the axial groovecomprising a smooth groove surface formed back away from the innercircumferential surface toward a radially outer side of the halfbearing, the groove surface defining a convex curve toward the radiallyouter side in a cross-section perpendicular to an axial direction of thehalf bearing and defining a straight line extending in the axialdirection in a cross-section parallel to the axial direction, whereinthe half bearing further comprises a plurality of circumferential narrowgrooves and a plurality of axial narrow grooves that are formed on thegroove surface so as to be back away from the groove surface toward theradially outer side, the plurality of circumferential narrow grooves andthe plurality of axial narrow grooves extending in a circumferentialdirection and the axial direction of the half bearing, respectively, soas to cross each other, and a depth of the axial narrow groove from thegroove surface is greater than a depth of the circumferential narrowgroove from the groove surface, and a width of the axial narrow grooveon the groove surface is greater than a width of the circumferentialnarrow groove on the groove surface.
 2. The half bearing according toclaim 1, wherein a depth of the axial groove from the innercircumferential surface is 2 to 50 μm.
 3. The half bearing according toclaim 2, wherein the depth of the circumferential narrow groove from thegroove surface is 0.05 to 3 μm, the width of the circumferential narrowgroove on the groove surface is 5 to 85 μm, and a pitch of thecircumferential narrow grooves is 5 to 100 μm.
 4. The half bearingaccording to claim 2, wherein the depth the axial narrow groove from thegroove surface of the axial groove is 0.3 to 10 μm, the width of theaxial narrow groove on the groove surface is 10 to 150 μm, and a pitchof the axial narrow grooves is 10 to 200 μm.
 5. The half bearingaccording to claim 1, wherein a plurality of the axial grooves areformed on the inner circumferential surface.
 6. The half bearingaccording to claim 5, wherein the plurality of axial grooves are formedsubstantially at equal intervals in the circumferential direction. 7.The half bearing according to claim 1, wherein the axial groove does notopen at any axial end surface of the half bearing.
 8. A cylindricalsliding bearing for supporting a crankshaft of an internal combustionengine, comprising the half bearing according to claim
 1. 9. The slidingbearing according to claim 8, consisting of a pair of the half bearings.